1. Field of the Invention
The present invention is generally related to a hydraulically actuated marine transmission and, more particularly, to a marine propulsion device which utilizes a solenoid and associated spool valve to direct the flow of hydraulic fluid to various portions of an actuating hydraulic cylinder, wherein the spool valve is located in the structure of a marine gear case.
2. Description of the Related Art
Those skilled in the art of marine propulsion systems and marine transmissions are aware of many different applications of hydraulic power to shift a marine transmission between forward, neutral, and reverse gear positions.
U.S. Pat. No. 3,623,583, which issued to Shimanckas on Nov. 30, 1971, describes an electrically operated control mechanism for a hydraulic shifting mechanism. A marine propulsion unit or drive includes a hydraulic mechanism which is operative to effect shifting of a clutch from a fail-safe forward drive condition to either a neutral or reverse condition. It also describes an electrically operated control mechanism for the hydraulic mechanism. The control mechanism is also designed to fail-safe in forward drive position. The control mechanism includes aligned, neutral and rearward drive solenoids which are selectively energizeable to afford neutral and reverse drive and which are operably associated with a single plunger carrying a spool valve embodied in the hydraulic system.
U.S. Pat. No. 3,752,281, which issued to Arnold on Aug. 14, 1973, describes reversing clutches with selector and pressure modulating valve. A power transmission including a forward, friction plate, modulating type friction clutch, a reverse modulating type clutch, and a selector control valve assembly. The assembly has a rotatable selector spool that acts to select the proper direction of the travel for the water craft or vehicle with which it is used.
U.S. Pat. No. 3,919,964, which issued to Hagen on Nov. 18, 1975, describes a marine propulsion reversing transmission with a hydraulic assist. The reversing transmission is located in a propulsion unit and connects a driveshaft to a propeller shaft. It is shiftable between neutral, forward drive, and rearward drive conditions.
U.S. Pat. No. 3,944,035, which issued to McRay on Mar. 16, 1976, describes a fluid control system for a hydraulically operated transmission and master clutch. The device is described in relation to a motor grader and comprises a normally engaged main engine clutch, a high-low power clutch range transmission, and a four speed reversible power shift main transmission. The main engine clutch is releasable manually by a clutch pedal or releasable automatically by a hydraulically operated clutch release cylinder.
U.S. Pat. No. 4,698,035, which issued to Ferguson on Oct. 6, 1987, describes a marine propulsion device hydraulic system. The device comprises a propulsion unit adapted to be pivotally mounted on the transom of a boat for pivotal movement relative to the transom about a steering axis. It includes a rotatably mounted propeller, an engine including a throttle lever, and a shiftable transmission drivingly connecting the engine to the propeller and including a shift lever.
U.S. Pat. No. Re. 36,342, which issued to McFadyen et al. on Oct. 19, 1999, describes a low deadband marine hydraulic steering system. A lock valve for marine hydraulic steering systems includes a valve body with a spool valve reciprocally received in a bore therein. A first port and a second port of the valve are connected to a manual pump. A third port and fourth port are connectable to a double acting hydraulic cylinder connected to a rudder or steerable motor. There are valves with the lock valve which normally prevent fluid flowing between the ports so the steering system remains in a fixed position when the helm is released. Fluid can flow from the first port to the third port when the first port is pressurized. A return flow of fluid from the fourth port to the second port is permitted only when the first nozzle is pressurized.
U.S. Pat. No. 6,062,926, which issued to Alexander et al. on May 16, 2000, discloses a hydraulic system for a dual propeller marine propulsion unit. A vertical driveshaft is operably connected to the engine of the propulsion unit and carries a pinion that drives a pair of coaxial bevel gears. An inner propeller shaft and an outer propeller shaft are mounted concentrically in the lower torpedo section of the gear case and each propeller shaft carries a propeller. To provide forward movement for the watercraft, a sliding clutch is moved in one direction to operably connect the first of the bevel gears with the inner propeller shaft to drive the rear propeller. A hydraulically operated multi-disc clutch is actuated when engine speed reaches a preselected elevated value to operably connect a second of the bevel gears to the outer propeller shaft, to thereby drive the second propeller in the opposite direction.
U.S. Pat. No. 6,884,131, which issued to Katayama et al. on Apr. 26, 2005, describes a shift mechanism for a marine propulsion unit. An outboard motor incorporates a driveshaft and a propulsion shaft driven by the driveshaft. The driveshaft carries a pinion. The propulsion shaft carries forward and reverse gears. The pinion always meshes with the forward and reverse gear and drives the forward and reverse gears in opposite directions relative to each other. A hydraulic forward clutch mechanism couples the forward gear with a propulsion shaft. A hydraulic reverse clutch mechanism couples the reverse gear with the propulsion shaft. A shift actuator selectively operates the forward clutch mechanism or the reverse clutch mechanism to provide forward, reverse and/or neutral running conditions for the outboard motor.
U.S. Pat. No. 7,162,946, which issued to Jeon on Jan. 16, 2007, describes a hydraulic control valve having a holding valve with improved response characteristics. The hydraulic control valve includes a valve housing including a pump path communicating with a hydraulic pump, a tank path communicating with an oil tank, and first and second cylinder ports communicating with a hydraulic cylinder, a control spool movably provided in the valve housing, cutting the pump to path off the first and second cylinder ports in a neutral state and selectively connecting the pump path and the tank path with the first and second cylinder ports while moving in left and right directions if pilot signal pressures are applied thereto. It also comprises a holding valve provided between the second cylinder port and the control spool, cutting out the second cylinder port when the control spool is in a neutral state and holding load of the hydraulic cylinder so as not to cause natural drop of the hydraulic cylinder. It also provides an actuating path for the holding valve connecting hydraulic oil of the second cylinder port to the tank path when the control spool is in a neutral state.
U.S. Pat. No. 7,291,048, which issued to Phillips et al. on Nov. 6, 2007, discloses an actuator device for a marine propulsion transmission. An actuator of a marine propulsion transmission is attached to a movable clutch member through the use of a coupler which comprises a generally spherical member formed as a portion of the actuator and a check device formed as part of the clutch member. The generally spherical member, or alternatively shaped component, is received by the check device and retained therein. The components are configured to allow relative rotation between the actuator and the clutch member while causing them to move axially in synchrony with each other.
U.S. patent application Ser. No. 11/893,746 (M10122), which was filed on Aug. 17, 2007 by Phillips et al., discloses an actuator for a marine transmission which uses four cavities of preselected size in order to provide four potential forces resulting from pressurized hydraulic fluid within those cavities. The effective areas of surfaces acted upon by the hydraulic pressure are selected in order to provide increased force to move the actuator toward a neutral position from either a forward or reverse gear position. Also, the relative magnitudes of these effective areas are also selected to provide a quicker movement into gear than out of gear, given a similar differential magnitude of pressures within the cavities.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
It would be significantly beneficial if a marine transmission could be provided with a spool valve contained within the gear case of the transmission and configured to conduct pressurized oil to and from a hydraulic piston system in a way which takes advantage of all of the capabilities of the hydraulically actuated transmission.